The apicomplexan parasites Cryptosporidium parvum and Cryptosporidium hominis are major etiologic agents of cryptosporidiosis in humans. Infection is typically self-limited in immunocompetent adults, but it can lead to chronic and fulminant disease in immunocompromised patients, as well as malnutrition and stunting in children. Nitazoxanide is the current standard of care for cryptosporidiosis, but the drug only exhibits partial efficacy in children and is no more effective than placebo in AIDS patients. Unfortunately, the development of novel therapeutics for cryptosporidiosis has proven to be extremely difficult as a result of the financial obstacles that plague drug discovery for diseases that disproportionately affect the developing world, as well as technical limitations associated with the laboratory study of Cryptosporidium parasites.
While cryptosporidiosis is a significant cause of self-limited diarrhea in immunocompetent individuals who may be exposed to parasites through contaminated municipal and recreational water supplies or through occupational exposures, the burden of cryptosporidiosis is even more substantial in immunocompromised and pediatric populations. Immunodeficient individuals, including patients maintained on immunosuppressive regimens following organ transplantation and AIDS patients, in particular, risk developing chronic, fulminant, and sometimes fatal disease (especially when CD-4+ T-cell counts drop below 50 cells/mm3). Diarrhea is also a leading cause of death in children under 5 years of age, and the recent Global Enteric Multicenter Study (GEMS) identified Cryptosporidium as a major cause of life-threatening diarrhea during the first two years of life. Moreover, cryptosporidiosis has been associated with malnutrition and persistent deficits in development in this population.